High purity gas distribution systems, such as are used in semiconductor manufacturing or other thin film coating processes, typically include a source of high purity gas coupled through a series of gas processing elements such as a mass flow controller, pressure sensor and/or regulator, heater, filters or purifiers, and shutoff valves. In semiconductor processing, a series-connected set of such elements is referred to as a "gas stick". In a typical semiconductor processing apparatus, multiple gas sources are connected to the chamber through multiple gas sticks, which are typically mounted to a frame, forming a complete assembly known as a "gas box".
As the dimensions of semiconductor devices decrease and their density increases, semiconductor manufacturing processes have become increasingly intolerant of particulate contamination. One important source of such contamination is the gasses used during the process, and particularly particulate carried by the wetted surfaces of the gas stick which delivers gas from the source to the chamber. Moisture or dust which accumulates within a gas stick or processing component will be carried with the source gas and deposit onto the semiconductor devices being processed, creating defects. Moisture also may corrode the wetted surfaces, leading to flaking of particles from these surfaces.
To reduce contamination of this sort, gas sticks and gas processing components for semiconductor processing are manufactured in low-dust, low-moisture environments, and purged for lengthy periods of time at elevated pressures after manufacture. Furthermore, gas processing components are typically packaged and sealed in pressurized nitrogen for shipment. As a result, the interior of the component or stick is exposed only to the clean room environment in which the semiconductor processing equipment is located, and only for the brief period of time between removal of the packaging and sealing of the stick or component into the processing equipment.
Despite these careful handing procedures, even brief exposure of a gas stick or component to clean room air results in the accumulation of potentially damaging levels of particulate and moisture within the stick or component, requiring extensive purging of the gas stick after assembly, and prior to further use for semiconductor manufacturing. Because the semiconductor manufacturing equipment cannot operate during purging, the time needed for purging represents substantial lost revenue.
The gas processing components in a gas stick, and other components and connections in the gas distribution system, will wear and need replacement at various frequencies throughout the life of the processing apparatus. Typically, a component is replaced by closing the valves most nearly adjacent to the component, uncoupling and replacing the component, and reopening the adjacent valves. To simplify this operation and minimize the extent of the gas stick exposed to room air during this procedure, each component is typically connected to its neighboring components or tubing with removable couplers, and valves are placed between components at several locations along the stick. Nevertheless, the act of uncoupling a component or portion of the stick and removing it from the stick exposes that component and the replacement component to room air, and also exposes substantial wetted surface between the component and the nearest valves (including the inside of any connecting tubing, and potentially other components), to room air. Thus, the gas stick must be extensively purged when the components are reassembled.